Revolutionary discovery: Vaporizing electronic waste reduces costs and recovers precious metals.

Innovative Metal Recovery from Electronic Waste

By instantly heating electronic devices to 3,000°C with an electrical current, scientists have discovered a way to extract high-quality precious metals without generating hazardous waste.

According to their analysis, using electronic waste as a source of precious metals could be up to 13 times cheaper than traditional mining extraction. However, previous methods required placing damaged devices in an oven that consumed large amounts of energy and emitted toxic substances into the air.

In contrast, the “instant joule heating” method uses electrical currents to vaporize valuable metals from the materials that make up electronic devices, being between 80 and 500 times more energy efficient.

A 2008 study estimated that one ton of mobile phones without batteries contains approximately 130kg of copper, 3.5kg of silver, 340 grams of gold and 140 grams of palladium.

These quantities, if analyzed in a mine drilling survey, would be considered world-class results, ranking in the 99th percentile for quality.

Most open pit mining operations manage extraction rates of between 0.5 and 1.8 grams of gold per ton and between 100 and 180 grams of silver per ton. With 40 million tons of e-waste produced annually, some simple math reveals the economic potential of collecting this waste for metals, a process scientists have dubbed “urban mining.”

Rice University scientists shredded a printed circuit board for their experiments and mixed it with carbon black as a conductive additive. Once in the instantaneous joule chamber, the applied current is so high that precious metals, such as rhodium, copper, and gold, briefly vaporize, while carbon-based components, such as plastic, carbonize. This same process has been used to turn plastic into diamonds.

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Base and precious metals mining companies use a variety of proprietary recovery processes to separate gold, zinc or nickel from the ore body.

As in mining, additives improved the recovery rate of metals from their vaporized form, including halides or fluoride-based substances. These increased the recovery of rhodium to more than 80%, and of palladium to 70%. Bleach and other chlorine-based compounds raised the silver recovery rate to over 80% as well.

With prices for these metals skyrocketing recently, new and cheaper sources will be crucial to ensuring important industries remain intact and competitive.

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